1. Field of the Invention
This invention relates generally to devices which grip and rotate pipe or hold pipe against rotational forces and, more particularly, to the components of such devices which make contact with the pipe.
2. Prior Art
There are many devices and mechanisms now on the market which are utilized to grip and rotate pipe. Some operate manually, while others are power assisted. In oil and gas drilling operations, it is necessary to grip drill pipe with extremely high compressive forces while applying a high degree of torque in order to break apart threaded pipe connections. In order to develop the desired forces, power tongs have been designed for gripping and rotating pipe. Examples of power tongs may be seen in the following U.S. patents: U.S. Pat. No. 4,290,304; U.S. Pat. No.4,404,876; U.S. Pat. No. 4,082,017; U.S. Pat. No. 4,084,453; U.S. Pat. No. 4,089,240.
As can be seen in the above listed patents, the actual contact with the pipe is accomplished through the use of die inserts which are pressed into some type of jaw member. When the power tong is in operation the die inserts are urged against the drill pipe and torque is applied. Examples of various configurations of die inserts may be found in FIG. 4 of U.S. Pat. No. 4,404,876 (see reference numerals 144,148 and 149), FIG. 5 of U.S. Pat. No. 4,082,017 (see reference numeral 34), and in FIGS. 4 and 5 of U.S. Pat. No. 4,290,304 (see reference numeral 92). As can be seen, the die inserts are relatively narrow in comparison to the jaw members to which they are attached, as well as to the total area of pipe covered by the jaw members. The die inserts are mostly commonly held in place through a dovetail key arrangement. Those die insert configurations illustrated above are virtually a standard in the industry.
Problems have developed with the above mentioned jaw/die configurations. The small wearing surfaces of prior art dies result in tremendous pressures (per unit of area) being applied to the drill pipe. These pressures result in deformation of the pipe, which in turn results in down time and pipe replacement costs. This is especially true in deep water drilling operations, where lightweight pipe must be utilized. Also, as torque is applied, the dovetail keyway of prior art dies will wear due to the small surface area which must bear the torque, necessitating expensive replacement of the entire jaw/die assembly. Because of the small wearing surface of the dies, they are also prone to quickly wear out. The above problems were necessitated by the belief that the die size must remain small in comparison to the jaw member in order to provide the necessary bulk to resist the amount of torque which is applied to the pipe.